Answer: 10 rotis
Explanation:
To find the number of rotis per meal that Varun and Rosa take, we can break down the information given in the question. Let's say Varun takes x rotis per meal. Since he always wastes half a roti, he actually consumes (x - 0.5) rotis per meal. Rosa takes half the number of rotis as Varun, so she takes (x / 2) rotis per meal. Now, let's calculate the number of rotis consumed by both of them in 20 days. Since they have lunch every day, the total number of rotis consumed by Varun in 20 days would be (20 * (x - 0.5)). Similarly, the total number of rotis consumed by Rosa in 20 days would be (20 * (x / 2)). According to the question, the total number of rotis consumed by them together in 20 days is 120. So, we have the equation: (20 * (x - 0.5)) + (20 * (x / 2)) = 120. Simplifying the equation, we get: 20x - 10 + 10x = 120. Combining like terms, we get: 30x = 130. Dividing both sides by 30, we find that x = 4.33. Since we cannot have a fraction of a roti, we can conclude that Varun takes 4 rotis per meal and wastes 0.5 roti, while Rosa takes 2 rotis per meal and finishes her share. To find the number of rotis wasted in 20 days, we can multiply the number of wasted rotis per meal by the number of meals in 20 days. In this case, Varun wastes 0.5 roti per meal, so in 20 days, he would waste (20 * 0.5) = 10 rotis.